This invention relates to anti-ice systems particularly of the type used for preventing icing of structural components in aircraft. More specifically, the invention relates to an improved anti-ice system for optimizing the flow of heated air to aircraft components during icing conditions.
Icing of aerodynamic structural components such as wings comprises a major problem in the operation of aircraft in cold weather conditions. Accordingly, to prevent icing of these structural components, it is well known to provide a source of heated air for circulation to the component subject to icing. The heated air sufficiently elevates the surface temperature of the structural component so as to prevent the formation of ice thereon.
Various anti-ice control systems have been devised in the prior art for providing a supply of heated air to aircraft structural components subject to icing. Among the more effective of these systems comprises an auxiliary combustion heater, such as that shown and described in British Pat. No. 673,961. However, combustion heaters consume fuel from the aircraft main engine fuel system, and present problems such as increased weight, complexity, fire hazard, and carbon monoxide poisoning.
In turbine engine-powered aircraft, it is known to bleed off a portion of the hot compressed air output of the engine compressor, and to supply this so-called bleed air to the structural components to prevent the formation of ice. However, uncontrolled supply of the bleed air to the structural components reduces the quantity of hot compressed air available for supply to the engine, and thereby has a detrimental effect upon engine performance. Accordingly, various bleed air systems have been proposed to control the supply of bleed air to these structural components. Some of these systems comprise, for example, a manually operated control such as that disclosed in U.S. Pat. No. 3,258,229. Other bleed air systems have controlled the quantity of bleed air in response to the pressure of the bleed air, or in response to the temperature of the bleed air, or in response to a combination of these parameters. See, for example, U.S. Pat. Nos. 3,058,695; 3,749,336; 2,563,054; 3,057,154; 2,648,193; and 2,868,483. However, these prior art systems have not satisfactorily optimized the control of the bleed air supply so that a minimum quantity of bleed air sufficient for preventing the formation of ice is supplied to the structural components.
The invention of this application overcomes the problems and disadvantages of the prior art by providing an improved anti-ice control system for optimizing the supply of bleed air to structural components to a minimum quantity sufficient to prevent the formation of ice.